Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 21839-2008 Steel for prestressed concrete - Test methods. In addition to a number of editorial changes, the following technical changes have been made with respect to GB/T 21839-2008:
——The normative references are modified (see Clause 2; Clause 2 of Edition 2008);
——Some symbols are modified and added (see Clause 3; Clause 3 of Edition 2008);
——The general provisions concerning test pieces are modified (see Clause 4; Clause 4 of Edition 2008);
——Tensile test is modified; requirements for tensile test pieces are added, parameters A and Z are added for the measurement in tensile test, artificial method is added for the measurement of Agt according to GB/T 228.1; measurement of modulus of elasticity (E) is refined (see 5.3.2);
——Judgment of the bend test result is modified (see 6.4; 6.4 of Edition 2008);
——Equipment for reverse bend test is added (see 7.2);
——Adhesion test of coating is added (see Clause 9);
——Relevant technical requirements of extensometer are modified (see Clause 5 and Annex C; Clause 5 and Annex A of Edition 2008);
——Safety warning for chemical reagents is added at the part of stress corrosion test solution (see 12.3.5);
——Requirements for length of indentation are added (see 15.3.2.4);
——Testing of the content of anti-corrosive grease is added (see Clause 18);
——Measurement of sheath thickness is added (see Clause 19);
——Test for uniformity of coating is added (see Clause 20);
——Test for quality of zinc coating is added (see Clause 21).
This standard has been redrafted and modified in relation to ISO 15630-3:2010 Steel for the reinforcement and prestressing of concrete - Test methods - Part 3: Prestressing steel.
Many structural adjustments have been made with respect to ISO 15630-3:2010, and a comparison table between this standard and ISO 15630-3:2010 in clause/subclause number is listed in Annex A.
This standard includes technical differences with respect to ISO 15630-3:2010. The clauses and subclauses concerned are identified by a vertical single line (|) located in the blank on its external margin of the page. These technical differences and their causes are listed in Annex B.
In addition, the following editorial changes have been made in this standard:
——“Annex A (informative) Comparison between this standard and ISO 15630-3:2010 in clause/subclause number” is added;
——“Annex B (Informative) Technical differences and their causes between this standard and ISO 15630-3: 2010” is added.
——“Annex C (Informative) Methods for tensile test of strand for prestressing concrete” is added.
This standard was proposed by China Iron and Steel Industry Association.
This standard is under the jurisdiction of the National Technical Committee on Iron and Steel of Standardization Administration of China (SAC/TC 183).
The previous edition of this standard is as follows:
—GB/T 21839-2008.
Test methods of steel for prestressing concrete
1 Scope
This standard specifies the methods concerning tensile test, bend test, reverse bend test, torsion test, adhesion test of winding and coating, isothermal relaxation test, axial force fatigue test, stress corrosion test in a solution of thiocyanate, deflected tensile test, determination of chemical composition, measurement of the geometrical dimension, determination of the relative rib area, determination of deviation from nominal weight per metre, testing of the content of anti-corrosive grease, measurement of sheath thickness, test for uniformity of coating and test for quality of galvanized coating, etc. of steel for prestressing concrete.
This standard is applicable to the determination of properties related prestressing steel wire, prestressing steel rod, prestressing steel bar, prestressing steel strand and other products.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature (GB/T 228.1-2010, ISO 6892-1:2009, MOD)
GB/T 230.1 Metallic materials - Rockwell hardness test - Part 1: Test method (GB/T 230.1-2018, ISO 6508-1:2016, MOD)
GB/T 232 Metallic materials - Bend test (GB/T 232-2010, ISO 7438:2005, MOD)
GB/T 238 Metallic materials - Wire - Reverse bend test (GB/T 238-2013, ISO 7801:1984, MOD)
GB/T 239.1 Metallic materials - Wire - Part 1: Simple torsion test (GB/T 239.1-2012, ISO 7800:2003, MOD)
GB/T 1839 Test method for gravimetric determination of the mass per unit area of galvanized coatings on steel products (GB/T 1839-2008, ISO 1460:1992, MOD)
GB/T 2972 Test method for uniformity of zinc coating on zinc-coated steel wire by the copper sulphate dip (GB/T 2972-2016, ISO 7989-2:2007, NEQ)
GB/T 2975 Steel and steel products - Location and preparation of samples and test pieces for mechanical testing (GB/T 2975-2018, ISO 377:2017, MOD)
GB/T 2976 Metallic materials - Wire - Wrapping test (GB/T 2976-2004, ISO 7802:1983, IDT)
GB/T 3505 Geometrical product specifications (GPS) - Surface texture: Profile method - Terms definitions and surface texture parameters (GB/T 3505-2009, ISO 4287:1997, IDT)
GB/T 4336 Carbon and low-alloy steel - Determination of multi-element contents - Spark discharge atomic emission spectrometric method (routine method)
GB/T 12160 Calibration of extensometers used in uniaxial testing (GB/T 12160-2002, ISO 9513:1999, IDT)
GB/T 16825.1 Verification of static uniaxial testing machines - Part 1: Tension/compression testing machines - Verification and calibration of the force-measuring system (GB/T 16825.1-2008, ISO 7500-1:2004, IDT)
3 Symbols and definitions
For the purposes of this document, the symbols given in Table 1 apply.
Table 1 Symbols and their description
Symbol Unit Description Reference
am mm Rib height at the mid-point 15.3, 16.2
amax mm Maximum depth of indentation or height of rib 15.3
as,i mm Average height of a rib in unit length ?l 16.2
a1/4 mm Rib height at the quarter-point 15.3, 16.2
a3/4 mm Rib height at the three-quarters point 15.3, 16.2
A % Percentage elongation after fracture 5.3.1
Agt % Percentage total elongation at maximum force 5
At % Total elongation at break 5.3.1
b mm Width of transversal rib 15.3.1.6
c mm Rib or indentation spacing 15.3
C mm Groove width of the mandrel used for the deflected tensile test 13.3.4
d mm Nominal diameter of the rod, wire or strand 11.2, 11.4.6, 12.3.4
da mm Nominal diameter of the mandrel used for the deflected tensile test 13.3.4
db mm Diameter with 2 gauge cylinders in the groove of the mandrel used for the deflected tensile test 13.3.4
de mm Diameter of the gauge cylinder used for the deflected tensile test 13.3.4
dg mm Diameter of guide hole 7.3
di mm Inner diameter of the groove of the mandrel used for the deflected tensile test 13.3.4
D % Average coefficient of reduction of the maximum force in the deflected tensile test 13.2, 13.4
Dc mm Inner diameter of the cell in the stress corrosion test 12.3.4
Di % Individual percentage of reduction of the maximum force in the deflected tensile test 13.4
e mm Average gap between two adjacent ribs or indentation rows 15.3.1.4, 15.3.2.4
E GPa Modulus of elasticity 5.3
f HZ Frequency of force cycles in the axial force fatigue test 11.1, 11.4.2
fR — Relative rib area 16
Fa,i N Individual breaking force in the deflected tensile test 13.4
Fm N Maximum force 5.3
N Mean value of the maximum force 10.2, 12.2, 13.2
Fp0.1 N 0.1% proof force 5.3
Fp0.2 N 0.2% proof force 5.3
Fr N Force range in the axial force fatigue test 11.1, 11.3, 11.4.2
Frt N Residual force in the test piece at time t in the relaxation test 10.1
ΔFrt N Force loss in the test piece at time t in the relaxation test 10.1
FR mm2 Area of longitudinal section of one transverse rib 16.2
Fup N Upper force in the axial force fatigue test 11.1, 11.3, 11.4.2
F0 N Initial force in the stress relaxation test and the stress corrosion test 10.1, 10.3, 10.4, 12.4.2
G mm Depth of the groove of the mandrel used for the deflected tensile test 13.3.4
h mm Distance from the top of cylindrical supports to the bottom of the guide 7.2
hb mm Bow height of the plane of prestressing steel 15.3.4
Lt mm Length of the test piece in the stress corrosion test 12.2
L0 mm Original gauge length in the isothermal relaxation test
Length of the test piece in contact with the solution in the stress corrosion test 10.1, 10.3, 10.4, 12.2, 12.3.4, 12.4.5
ΔL0 mm Elongation of the gauge length, L0, under force, F0, in the isothermal stress relaxation test 10.1, 10.3, 10.4
L'0 mm Determined original gauge length of Agt 5.3
L'u mm Determined gauge length after fracture of Agt 5.3
L1 mm Length of the passive side in the deflected tensile test 13.3.2
L2 mm Length of the active side in the deflected tensile test 13.3.2
m, n — Coefficients or numbers 10.4.9, 15.3, 16.2
P mm Lay length of a strand 15.3.3
R mm Corner radius at the base of the groove of the mandrel used for the deflected tensile test 13.3.4
r mm Radius of cylindrical supports 7.2
Ra μm Surface roughness of the mandrel used for the deflected tensile test 13.3.4
Sn mm2 Nominal cross-sectional area of the test piece 5.3.2
ta h Maximum agreed time for the stress corrosion test 12.4.5
tf,i h Individual lifetime to fracture in the stress corrosion test 12.4.5
h Median lifetime to fracture in the stress corrosion test 12.4.6
t0 s Starting time in the isothermal stress relaxation test and in the stress corrosion test 10.4.2, 12.4
V0 mm3 Volume of test solution to fill the test cell in the stress corrosion test 12.4.3
W g/m Weight of unbonded prestressing steel strand per metre 18.3
W1 g/m Weight of steel strand after removing the sheath and anti-corrosive grease from unbonded prestressing steel strand per metre 18.3
W2 g/m Weight of sheath after removing the anti-corrosive grease from unbonded prestressing steel strand per metre 18.3
W3 g/m Weight of anti-corrosive grease in unbonded prestressing steel strand per metre 18.3
Z % Percentage reduction of area 5.3.1
α (°) Angle of deviation in the deflected tensile test 13.3.2
β (°) Transverse rib or indentation angle to the bar or wire axis 15.3
εx — Value of the strain for a force equal to x 5.3.2
ρ % Relaxation 10.4.8
Σei mm Circumference of transverse rib gap 15.3.1.4, 15.3.2.4, 16.2
Note: 1N/mm2=1MPa
4 General provisions concerning test pieces
Unless otherwise agreed or specified in the product standard, the test pieces shall be taken from the finished product normally before packaging.
Special care should be taken when sampling is made from the packaged product (e.g. coil or bundle), in order to avoid plastic deformation which could change the properties of the samples used to provide the test pieces.
Specific complementary provisions concerning the test pieces may be indicated in the relevant clauses of this standard, if applicable.
5 Tensile test
5.1 Test pieces
?In addition to the general provisions given in Clause 4, the free length of the test piece shall be sufficient for the determination of the percentage total elongation at maximum force (Agt) in accordance with 5.3.1.
If the percentage elongation after fracture is determined manually, the test piece shall be marked in accordance with GB/T 228.1.
If the percentage total elongation at maximum force (Agt) is determined by the manual method for bar or wire, equidistant marks shall be made on the free length of the test piece (see GB/T 228.1). The distance between the marks shall be 20mm, 10mm or 5mm, depending on the test piece diameter.
Foreword i
1 Scope
2 Normative references
3 Symbols and definitions
4 General provisions concerning test pieces
5 Tensile test
6 Bend test
7 Reverse bend test
8 Torsion test
9 Adhesion test of winding and coating
10 Isothermal relaxation test
11 Axial force fatigue test
12 Stress corrosion test in a solution of thiocyanate
13 Deflected tensile test
14 Chemical analysis
15 Measurement of the geometrical dimension
16 Determination of the relative rib area (fR)
17 Determination of deviation from nominal weight per metre
18 Testing of the content of anti-corrosive grease
19 Measurement of sheath thickness
20 Test for uniformity of coating
21 Test for quality of zinc coating
22 Test report
Annex A (Informative) Comparison between this standard and ISO 15630-3: 2010 in clause/subclause number
Annex B (Informative) Technical differences and their causes between this standard and ISO 15630-3:
Annex C (Informative) Methods for tensile test of strand for prestressing concrete
預(yù)應(yīng)力混凝土用鋼材試驗(yàn)方法
1 范圍
本標(biāo)準(zhǔn)規(guī)定了預(yù)應(yīng)力混凝土用鋼材的拉伸、彎曲、反復(fù)彎曲、扭轉(zhuǎn)、纏繞和鍍層附著力、等溫松弛、軸向力疲勞、硫氰酸鹽溶液中的應(yīng)力腐蝕、偏斜拉伸、化學(xué)分析、幾何尺寸測量、相對肋面積確定、每米公稱質(zhì)量偏差的確定、防腐潤滑脂含量檢測、護(hù)套厚度測量、鍍層均勻性、鋅層質(zhì)量等試驗(yàn)方法。
本標(biāo)準(zhǔn)適用于預(yù)應(yīng)力鋼絲、預(yù)應(yīng)力鋼棒、預(yù)應(yīng)力鋼筋、預(yù)應(yīng)力鋼絞線等產(chǎn)品相關(guān)性能的測定。
2 規(guī)范性引用文件
下列文件對于本文件的應(yīng)用是必不可少的。凡是注日期的引用文件，僅注日期的版本適用于本文件。凡是不注日期的引用文件，其最新版本(包括所有的修改單)適用于本文件。
GB/T 228.1 金屬材料 拉伸試驗(yàn) 第1部分：室溫試驗(yàn)方法(GB/T 228.1—2010，ISO 6892-1：2009，MOD)
GB/T 230.1 金屬材料 洛氏硬度試驗(yàn) 第1部分：試驗(yàn)方法(GB/T 230.1—2018，ISO 6508-1：2016，MOD)
GB/T 232 金屬材料 彎曲試驗(yàn)方法(GB/T 232—2010，ISO 7438：2005，MOD)
GB/T 238 金屬材料 線材 反復(fù)彎曲試驗(yàn)方法(GB/T 238—2013，ISO 7801：1984，MOD)
GB/T 239.1 金屬材料 線材 第1部分：單向扭轉(zhuǎn)試驗(yàn)方法(GB/T 239.1—2012，ISO 7800：2003，MOD)
GB/T 1839 鋼產(chǎn)品鍍鋅層質(zhì)量試驗(yàn)方法(GB/T 1839—2008，ISO 1460：1992，MOD)
GB/T 2972 鍍鋅鋼絲鋅層硫酸銅試驗(yàn)方法(GB/T 2972—2016，ISO 7989-2：2007，NEQ)
GB/T 2975 鋼及鋼產(chǎn)品 力學(xué)性能試驗(yàn)取樣位置和試樣制備(GB/T 2975—2018，ISO 377：2017，MOD)
GB/T 2976 金屬材料 線材 纏繞試驗(yàn)方法(GB/T 2976—2004，ISO 7802：1983，IDT)
GB/T 3505 產(chǎn)品幾何技術(shù)規(guī)范(GPS) 表面結(jié)構(gòu) 輪廓法 術(shù)語、定義及表面結(jié)構(gòu)參數(shù)(GB/T 3505—2009，ISO 4287：1997，IDT)
GB/T 4336 碳素鋼和中低合金鋼 多元素含量的測定 火花放電原子發(fā)射光譜法(常規(guī)法)
GB/T 12160 單軸試驗(yàn)用引伸計(jì)的標(biāo)定(GB/T 12160—2002，ISO 9513：1999，IDT)
GB/T 16825.1 靜力單軸試驗(yàn)機(jī)的檢驗(yàn) 第1部分：拉力和(或)壓力試驗(yàn)機(jī)測力系統(tǒng)的檢驗(yàn)與校準(zhǔn)(GB/T 16825.1—2008，ISO 7500-1：2004，IDT)
3 符號及說明
表1給出的符號及說明適用于本文件。
表1 符號及說明
符號 單位 說明 涉及章條
am mm 中點(diǎn)肋高 15.3,16.2
amax mm 刻痕深度最大值/最高點(diǎn)肋高 15.3
as,i mm 肋在單位長度Δl上的平均高度 16.2
a1/4 mm 在1/4點(diǎn)處的肋高 15.3,16.2
a3/4 mm 在3/4點(diǎn)處的肋高 15.3,16.2
A % 斷后伸長率 5.3.1
Agt % 最大力總延伸率 5
At % 斷裂總延伸率 5.3.1
b mm 橫肋寬 15.3.1.6
c mm 肋或刻痕距 15.3
C mm 偏斜拉伸試驗(yàn)用的芯軸凹槽寬度 13.3.4
d mm 預(yù)應(yīng)力鋼棒、鋼絲、鋼絞線的公稱直徑 11.2,11.4.6,12.3.4
da mm 偏斜拉伸試驗(yàn)用芯軸公稱直徑 13.3.4
db mm 偏斜拉伸試驗(yàn)用兩量棒放在芯軸凹槽中的直徑 13.3.4
de mm 偏斜拉伸試驗(yàn)用量棒的直徑 13.3.4
dg mm 導(dǎo)向孔直徑 7.3
di mm 偏斜拉伸試驗(yàn)用芯軸凹槽的內(nèi)徑 13.3.4
D % 偏斜拉伸試驗(yàn)中最大力減少率的平均值 13.2,13.4
Dc mm 應(yīng)力腐蝕試驗(yàn)中容器內(nèi)徑 12.3.4
Di % 偏斜拉伸試驗(yàn)中單根試樣最大力減少的百分比 13.4
e mm 兩排相鄰的肋或刻痕之間的平均間隙 15.3.1.4,15.3.2.4
E GPa 彈性模量 5.3
f HZ 軸向疲勞試驗(yàn)中負(fù)荷循環(huán)頻率 11.1,11.4.2
fR — 相對肋面積 16
Fa,i N 偏斜拉伸試驗(yàn)中單根試樣破斷力 13.4
Fm N 最大力 5.3
N 最大力平均值 10.2,12.2,13.2
Fp0.1 N 0.1%屈服力 5.3
Fp0.2 N 0.2%屈服力 5.3
Fr N 軸向疲勞試驗(yàn)中力的范圍 11.1,11.3,11.4.2
Frt N 松弛試驗(yàn)t時間試樣上的剩余力 10.1
ΔFrt N 松弛試驗(yàn)t時間試樣松弛損失的力 10.1
FR mm2 橫肋軸向剖面面積 16.2
Fup N 軸向疲勞試驗(yàn)中的最大力 11.1,11.3,11.4.2
F0 N 應(yīng)力松弛試驗(yàn)和應(yīng)力腐蝕試驗(yàn)中的初始力 10.1,10.3,10.4,12.4.2
G mm 偏斜拉伸試驗(yàn)用芯軸凹槽深度 13.3.4
h mm 圓柱支座頂部至撥桿底部距離 7.2
hb mm 預(yù)應(yīng)力鋼材平面矢高 15.3.4
Lt mm 應(yīng)力腐蝕試驗(yàn)中試樣的長度 12.2
L0 mm 等溫松弛試驗(yàn)原始標(biāo)距，應(yīng)力腐蝕試驗(yàn)中試樣在溶液中的浸入長度 10.1,10.3,10.4
12.2,12.3.4,12.4.5
ΔL0 mm 等溫應(yīng)力松弛試驗(yàn)中在力F0時標(biāo)距L0的伸長 10.1,10.3,10.4
L'0 mm 測定Agt的原始標(biāo)距 5.3
L'u mm 測定Agt的斷后標(biāo)距 5.3
L1 mm 偏斜拉伸試驗(yàn)中固定端長度 13.3.2
L2 mm 偏斜拉伸試驗(yàn)中活動端長度 13.3.2
m,n — 系數(shù)或數(shù)字 10.4.9,15.3,16.2
P mm 鋼絞線捻距 15.3.3
R mm 偏斜拉伸試驗(yàn)中芯軸凹槽底部圓角半徑 13.3.4
r mm 圓柱支撐半徑 7.2
Ra μm 偏斜拉伸試驗(yàn)中芯軸表面粗糙度 13.3.4
Sn mm2 試樣公稱橫截面積 5.3.2
ta h 應(yīng)力腐蝕試驗(yàn)中最大規(guī)定時間 12.4.5
tf,i h 應(yīng)力腐蝕試驗(yàn)中單根試樣的斷裂時間 12.4.5
tf h 應(yīng)力腐蝕試驗(yàn)中試樣斷裂時間中值 12.4.6
t0 s 恒溫松弛試驗(yàn)和應(yīng)力腐蝕試驗(yàn)中開始時間 10.4.2,12.4
V0 mm3 應(yīng)力腐蝕試驗(yàn)容器中溶液的體積 12.4.3
W g/m 每米長無粘結(jié)預(yù)應(yīng)力鋼絞線的質(zhì)量 18.3
W1 g/m 每米長無粘結(jié)預(yù)應(yīng)力鋼絞線中除凈護(hù)套和防腐潤滑脂后的鋼絞線的質(zhì)量 18.3
W2 g/m 每米長無粘結(jié)預(yù)應(yīng)力鋼絞線中除凈防腐潤滑脂后的護(hù)套的質(zhì)量 18.3
W3 g/m 每米長無粘結(jié)預(yù)應(yīng)力鋼絞線中防腐潤滑脂的質(zhì)量 18.3
Z % 斷面收縮率 5.3.1
α (°) 偏斜拉伸試驗(yàn)中偏斜角度 13.3.2
β (°) 鋼棒或鋼絲的橫肋或刻痕與中心線的夾角 15.3
εx — X應(yīng)變支 5.3.2
ρ % 松弛率 10.4.8
Σei mm 橫肋間隙周長 15.3.1.4,15.3.2.4,16.2
注：1N/mm2=1MPa。
4 試樣的一般規(guī)定
除非另有其他協(xié)議或產(chǎn)品標(biāo)準(zhǔn)規(guī)定，試樣一般在成品包裝前在成品中截取。
當(dāng)樣品是包裝產(chǎn)品時(例如成卷或成捆)，截取試樣應(yīng)防止試樣因發(fā)生塑性變形而可能改變其性能。
必要時，可對本標(biāo)準(zhǔn)相關(guān)條款中試樣的要求進(jìn)行具體補(bǔ)充。
5 拉伸試驗(yàn)
5.1 試樣
試樣應(yīng)符合第4章的規(guī)定，測定最大力總延伸率(Agt)時，試樣的自由長度應(yīng)符合5.3.1的Agt相關(guān)要求。
手工法測定斷后伸長率時，按照GB/T 228.1要求劃等距離標(biāo)記。
用手工法測定鋼絲和鋼棒最大力總延伸率(Agt)時，在試樣自由長度上劃等距離標(biāo)記(見GB/T 228.1)，標(biāo)記間的距離根據(jù)樣品的直徑確定，可為20mm、10mm 或5mm。
5.2 試驗(yàn)設(shè)備
試驗(yàn)設(shè)備應(yīng)根據(jù)GB/T 16825.1進(jìn)行校驗(yàn)和校準(zhǔn)，并至少為1級準(zhǔn)確度。
測定E、Fp0.1或Fp0.2時，引伸計(jì)的準(zhǔn)確度應(yīng)為1級(見GB/T 12160)；用于測定Agt的引伸計(jì)可以為2級(見GB/T 12160)。
應(yīng)使用合適的夾具，避免試樣在夾具內(nèi)或在夾具附近斷裂。
5.3 試驗(yàn)程序
5.3.1 概述
5.3.1.1 拉伸試驗(yàn)應(yīng)按照GB/T 228.1的要求執(zhí)行；預(yù)應(yīng)力混凝土用多絲鋼絞線拉伸試驗(yàn)程序可參照附錄C執(zhí)行。
5.3.1.2 應(yīng)該使用引伸計(jì)測定彈性模量(E)，0.1%屈服力和0.2%屈服力(Fp0.1和Fp0.2)及最大力總延伸率(Agt)，引伸計(jì)的標(biāo)距按相關(guān)產(chǎn)品的標(biāo)準(zhǔn)要求確定。
5.3.1.3 Agt的精確值只能用引伸計(jì)來測得。如果試樣上的引伸計(jì)不能保持到試樣斷裂時，可按下列方法測定Agt：
——繼續(xù)加載直至引伸計(jì)記錄的伸長率稍大于Fp0.2時的伸長率，此時取下引伸計(jì)，記錄試驗(yàn)機(jī)上下工作臺的距離。繼續(xù)加載至試樣斷裂，記錄此時試驗(yàn)機(jī)上下工作臺的最終距離。
——計(jì)算出兩次試驗(yàn)機(jī)上下工作臺的距離之差，將此差值與試驗(yàn)機(jī)上下工作臺的初始距離之比和用引伸計(jì)測得的百分?jǐn)?shù)相加即為斷裂總延伸率At。
5.3.1.4 對于鋼絲、鋼棒、鋼筋A(yù)gt測定，應(yīng)按照下列方法進(jìn)行：
測量已拉伸試驗(yàn)過的試樣最長部分，測量區(qū)的范圍應(yīng)處于距離斷裂處至少5d，距離夾頭至少為2.5d。測量用的原始標(biāo)距應(yīng)等于產(chǎn)品標(biāo)準(zhǔn)中規(guī)定的值。
按下列式(1)計(jì)算：
(1)
式中：
L'u——測定Agt的斷后標(biāo)距；
L'0——測定Agt的原始標(biāo)距。
5.3.1.5 在裝引伸計(jì)前，宜給試樣預(yù)加一負(fù)荷，例如該預(yù)加負(fù)荷為試樣預(yù)期最大負(fù)荷的約10%。
5.3.1.6 如果Agt不是完全用引伸計(jì)測定的，應(yīng)在試驗(yàn)報(bào)告中注明。
5.3.1.7 拉伸性能值，F(xiàn)p0.1，F(xiàn)p0.2，F(xiàn)m均用力的單位表示。
5.3.1.8 斷后伸長率(A)測定原始標(biāo)距為試樣公稱直徑的8倍，除非相關(guān)產(chǎn)品標(biāo)準(zhǔn)另有規(guī)定。在有爭議的情況下，A 的測定采用手工法。
5.3.1.9 當(dāng)試樣在距夾具3mm 之內(nèi)發(fā)生斷裂，試驗(yàn)應(yīng)判為無效，應(yīng)允許重新試驗(yàn)。然而，如果所有試驗(yàn)數(shù)據(jù)大于等于相應(yīng)的規(guī)定值，其試驗(yàn)結(jié)果有效。
5.3.2 彈性模量的測定
在力-伸長率曲線中，用0.2Fm~0.7Fm范圍內(nèi)的直線段的斜率除以試樣的公稱橫截面積(Sn)測定彈性模量(E)。
(2)
斜率可以通過對測定數(shù)據(jù)進(jìn)行線性回歸得出，也可以用最優(yōu)擬合目測法得出。
在一些特定情況下，例如預(yù)應(yīng)力鋼筋和鋼棒，上述方法不適用時，可在0.05Fm~0.7Fm范圍內(nèi)測定彈性模量。
(3)
除5.3.1規(guī)定的要求外，測定彈性模量時，在力值范圍內(nèi)應(yīng)力速率應(yīng)保持不變。
6 彎曲試驗(yàn)
6.1 試樣
試樣應(yīng)符合第4章規(guī)定。
6.2 試驗(yàn)設(shè)備
6.2.1 試驗(yàn)設(shè)備的彎曲原理如圖1所示。
注：圖1為彎曲設(shè)備的外形構(gòu)造，可以是芯軸1和支撐2旋轉(zhuǎn)，支座3被固定；也可以是支座3旋轉(zhuǎn)，支撐2或芯軸1被固定。
說明：
1——芯軸；
2——支撐；
3——支座；
D ——芯軸直徑。
圖1 彎曲設(shè)備的原理
6.2.2 彎曲試驗(yàn)也可以按GB/T 232用帶有支撐和芯軸的裝置來進(jìn)行。
6.3 試驗(yàn)程序
彎曲試驗(yàn)應(yīng)在10℃~35℃的溫度進(jìn)行，試樣應(yīng)沿著芯軸進(jìn)行彎曲。
彎曲角度和芯軸直徑應(yīng)符合相關(guān)產(chǎn)品標(biāo)準(zhǔn)的要求。
6.4 試驗(yàn)結(jié)果的判定
彎曲試驗(yàn)結(jié)果的判定應(yīng)符合相關(guān)產(chǎn)品標(biāo)準(zhǔn)的要求。
當(dāng)產(chǎn)品標(biāo)準(zhǔn)沒有規(guī)定時，若受彎曲部位無目視可見的裂紋，則判定該試樣為合格。
產(chǎn)生在肋的根部或刻痕上的表面裂縫屬于有效試驗(yàn)。裂縫深度應(yīng)不大于裂縫寬度。
7 反復(fù)彎曲試驗(yàn)
7.1 試樣
除符合第4章規(guī)定外，試樣的制備應(yīng)符合GB/T 238中的相關(guān)規(guī)定。
7.2 試驗(yàn)設(shè)備
試驗(yàn)設(shè)備應(yīng)符合GB/T 238中的相關(guān)規(guī)定。
公稱直徑10mm
